Adaptive comb filter circuit including a plurality of filters and a switching means which results in improved movement detection in television signals

Abstract

A moving detection circuit which has a difference level generator which includes at least a frame delay circuit, and a vertical correlation detector which is connected to the difference signal generator and including a plurality of filters connected to the difference signal generator. A switching circuit for selecting one of the plurality of filters is provided and a control circuit is connected to the vertical correlation detector so as to control the switching circuit in response to the output level of the vertical correlation detector.

We claim as my invention: 
     
       1. A moving detection circuit comprising, a difference signal generator which includes at least a frame delay circuit, a vertical correlation detector connected to said difference signal generator comprising; (1) a plurality of filters connected to said difference signal generator; (2) switching means connected to said plurality of filters so as to allow the output of one of said filters to be selected; (3) control means connected to said vertical correlation detector and controlling said switching means in response to the output level of said vertical correlation detector, and wherein said plurality of filters are low-pass filters which have different frequency response characteristics. 
     
     
       2. A moving detection circuit according to claim 1, further comprising a band-pass or highpass filter which is connected to said difference signal generator. 
     
     
       3. A moving detection circuit according to claim 1, wherein said difference signal generator comprises a frame delay circuit and a subtractor which is connected to the input and output of said frame delay circuit. 
     
     
       4. A moving detection circuit according to claim 3, wherein said frame delay circuit includes one horizontal line time delay circuit so as to supply a signal to said vertical correlation detector. 
     
     
       5. A moving detection circuit according to claim 3, wherein said frame delay circuit comprises a field memory which has a 263 horizontal line time delay, and a field memory which has a 262 horizontal line time delay. 
     
     
       6. A moving detection circuit comprising, a difference signal generator which includes at least a frame delay circuit, a vertical correlation detector connected to said difference signal generator comprising; (1) a plurality of filters connected to said difference signal generator; (2) switching means connected to said plurality of filters so as to allow the output of one of said filters to be selected; (3) control means connected to said vertical correlation detector and controlling said switching means in response to the output level of said vertical correlation detector, and wherein said plurality of filters include combinations of low-pass filters which have different frequency response characteristics. 
     
     
       7. A moving detection circuit according to claim 6, wherein said switching means consist of a plurality of switches which correspond to said combinations of low-pass filters. 
     
     
       8. A moving detection circuit according to claim 7, further comprising, an adder which is connected to the outputs of said plurality of switches. 
     
     
       9. A moving detection circuit according to claim 6, further comprising a plurality of band-pass or high-pass filters which are connected to said difference signal generator. 
     
     
       10. A moving detection circuit according to claim 9, further comprising a subtracter which is connected to the outputs of said plurality of band-pass or high-pass filters. 
     
     
       11. A moving detection circuit comprising, a difference signal generator which includes at least a frame delay circuit, a vertical correlation detector connected to said difference signal generator comprising; (1) a plurality of filters connected to said difference signal generator; (2) switching means connected to said plurality of filters so as to allow the output of one of said filters to be selected; (3) control means connected to said vertical correlation detector and controlling said switching means in response to the output level of said vertical correlation detector, and wherein said difference signal generator comprises three field delay circuits which are connected in series and two subtracters which are connected to said field delay circuits. 
     
     
       12. A moving detection circuit according to claim 11, wherein said three field delay circuits consist of first, second and third field delay circuits which are connected in series, and said two subtracters consist of a first subtracter which is connected to the input of said first field delay circuit and to the output of said second field delay circuit, and a second subtracter which is connected to the input of said second field delay circuit and to the output of said third field delay circuit. 
     
     
       13. A moving detection circuit according to claim 11, wherein one of said three field delay circuits includes one horizontal line time delay circuit so as to supply a signal to said vertical correlation detector. 
     
     
       14. A moving detection circuit comprising, a difference signal generator which includes at least a frame delay circuit, a vertical correlation detector connected to said difference signal generator comprising; (1) a plurality of filters connected to said difference signal generator; (2) switching means connected to said plurality of filters so as to allow the output of one of said filters to be selected; (3) control means connected to said vertical correlation detector and controlling said switching means in response to the output level of said vertical correlation detector, and wherein said difference signal generator comprises two field delay circuits which are connected in series and two subtractors of which one is connected to said two field delay circuits for generating field and frame difference signals.